Detent positioning device

ABSTRACT

This detent positioning device for orienting and locking a rotary member rigid with a cam in one or more angular positions comprises a roller follower engaging the contour of said cam and adapted to engage a notch under the control of a hydraulic actuator incorporating spring means in its piston rod and, between said rod and the roller, a strap rigid with the rod and a rocker pivoted to said strap and supporting the roller. The arrangement is such that in case of alignment of the three points consisting of the axis of rotation of said rotary member, of the cam dead center and of the axis of rotation of said roller, this alignment is broken automatically by the device.

United States Patent [1 1 Cottin Nov. 27, 1973 DETENT POSITIONING DEVICE[75] Inventor:

[73] Assignee:

Jean Claude Cottin, Paris, France Produmatic, Chateauneuf en Thymerais,France [22] Filed: Nov. 19, I971 [21] Appl. No.: 200,311

.If... W527 [51] Int. Cl GOSg 5/06 [58] Field of Search 74/495, 527, 569

[56] References. Cited UNITED STATES PATENTS 3,373,631 3/1968 Biabaud74/495 3,692,149 5/1971 Evans 74/814 3,001,416 9/1961 Kalbermatler74/527 Primary Examiner-Charles .l. Myhre Assistant Examiner-R. H.Lazarus Att0rneyAmster & Rothstein This detent positioning device fororienting and locking a rotary member rigid with a cam in one or moreangular positions comprises a roller follower engaging the contour ofsaid cam and adapted to engage a notch under the control of a hydraulicactuator incorporating spring means in its piston rod and, between saidrod and the roller, a strap rigid with the rod and a rocker pivoted tosaid strap and supporting the roller. The arrangement is such that incase of alignment of the three points consisting of the axis of rotationof said rotary member, of the cam dead center and of the axis ofrotation of said roller, this alignment is broken automatically by thedevice.

3 Claims, 8 Drawing Figures DETENT POSITIONING DEVICE FIELD OF THEINVENTION This invention relates in general to detent positioningdevices.

DESCRIPTION OF THE PRIOR ART simple it is objectionable in its variousknown forms of embodiment in that .the assembly is usually wedged whenthe roller carried by the actuator piston rod en.- gages the top deadcenter of the cam.

In fact, in these known devices and in this specific position the threepoints corresponding to the axis of rotation of the shaft or member tobe controlled, to the top dead center of the cam and to the axis ofrotation of the roller are aligned: therefore, no lateral componentforce is available for urging the cam (and all the more the shaft orother member rigid therewith) for rotation in one or the otherdirection.

SUMMARY OF THE INVENTION It is the essential object of the presentinvention to avoid the inconvenience set forth hereinabove by providingmeans whereby the above-definedthree points are put automatically out ofalignment when said top dead center position is attained.

To this end, the detent-positioning roller is carried by arockerpivotally mounted in a strap rigid with the outer end of theactuator piston rod, sa-Id rocker being responsive to the action ofspring means incorporated in said outer end of the piston rod.

In addition to the elimination of any possibility of wedging the partswhen the roller is clearing the top dead center position, this device isadvantageous in that it ensures an accurate detent positioning of therotary member in the angular position or positions contemplated when theroller engages a bottom dead center of said cam.

Further advantages and features of this invention will appear as thefollowing description proceeds with reference to the accompanyingdrawings illustrating diagrammatically by way of exarnpleaa typical formof embodiment of the device of this invention;

In the drawings:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a part-sectional,part-elevational view of the rotary member and its detent positioningdevice, the section being taken atright angles to the axisof said rotarymember and devices;

FIG. 2 is a part-sectional view, the section being taken along the lineII-II of FIG. 1;

FIGS. 3a, 3b, 30 show in fragmentary and diagrammatic views thepositions of the component elementsof the device obtainingduring threedifferent phases of the detent positioning of the rotary member in aselected angular position; and

FIGS. 4a and 4b are views similar to FIGS. 3a to 30 illustrating twophases of the operation taking place when the roller is clearing atopdead center of the cam.

DESCRIITION OF THE PREFERRED EMBODIMENT A rotary shaft 1 has rigidlysecured thereto a cam 2, in this specific example a heart-shaped camhaving its bottom dead center provided with a symmetric V shaped notch3.

Mounted in the structure 4 rotatably supporting the shaft 1 is anactuator 5 comprising (see FIG. 2) a cylinder 6, a bottom 7, a pistonand 8, a cylinder bottom packing seal 9, a piston packing in thecylinder, a piston-rod packing 11 in the cylinder, and a guide ring 13.A strap 15 secured to the outer end of piston rod 8 carries a rocker l6pivoted to said strap 15 about a pin 17, the angular excursion of thisrocker being restricted by a check pin 18. The rocker 16 rotatablycarries a roller follower 19 by means of a pin 20, a needle bearing 21being interposed between this pin andthe roller follower 19. The rocker16 is constantly urged against the cam,2 or the check pin 18 by astacking 22 of dishedtsprings guided by an axial rod 23 of a push member24, a hardened metal plate 25 and a ball 26 being interposed between thepush member 24 and rocker l6. v

The above-described device operates as follows When the piston 8 ismoved downwards by feeding fluid under pressure to the actuator chamber27, the shaft 1 can rotatefreely.

For a convenient analysis of the mode of controlling V the shaft], thefollowing forces will now be considered F force necessary for obtaininga resultant capable of rotatably driving the shaft 1. This force dependson the resistant torque of shaft 1 and on the slope of the cam outline;F force developed by the stacked springs 22 in their flat condition, andF, maximum thrust exerted by the actuator in the direction of the cam 2.

The construction according to this invention implies the requirementWhen fluidunder pressure is fed to chamber 27, assuming that the shaft 1is stationary, the assembly comprising the piston rod, the strap and therocker is moved bodily towards the cam and the roller follower 19engages the cam outline (FIG. If under these conditions, the roller 19engages the cam outline at a point other than its top dead center, sincethe force F alone is sufficient for controlling the cam rotation, thesprings 22 are substantially unstressed and the tocker 16 remains inengagement with the check pin 18.

The shaft 1 begins to rotate and this movement continues until theroller 19 engages the V-shaped notch 3 at the bottom dead center of cam2 (FIG. 3b). The rotational movement is discontinued, as the roller 19acts as a lock bolt in said V-shaped notch 3 of cam 2. The roller 19 isheld against motion together with the piston 8; therefore, the thrustexerted by the actuator increases up to amaximum force F,. Since thisforce F, is greater than the force F developed by the stacked springs22, these are compressed home, and the piston 8 and strap 15 continuetheir movement towards the cam, thus 'causing the rocker 16 to pivotabout its fulcrum pin 17 until its opposite end 29 abutes the bottom ofstrap 15. During this pivotal movement of rocker I6,

the roller 19 moves the cam 2 and shaft 1 to the right, as seen in thedrawing, to their final angular position. This position illustrated inFIG. 3c is extremely precise and reproducible since the roller positionis strictly subordinate to the dimensions of the triangle having itsapices at the point of contact between the roller follower 19 and thecam 2, the axis of pin 17 and the point of engagement of the rocker end29 with the strap bottom. The locking torque exerted on the shaft inthis position depends on the maximum value F,, and besides the angle ofthe V-notch 3 in the cam may be determined at will without taking intoaccount the value of F If the roller follower 19 engages the top deadcenter of cam 2 (FIG. 4a) the force F is applied to the point of contactbetween roller 19 and cam 2, and the shaft 1 is not rotated since thethree points, i.e., shaft center top dead center and roller axis, arealigned. The thrust exerted by the actuator then increases up to thevalue F,, the stacked springs 22 are compressed and the strap is moveddownwards. Then the rocker 16 pivots about its pin 17 and leaves thecheck pin 18 (FIG. 4b). During this rocker movement the point of contactof roller 19 with the cam outline is shifted to the right. Immediatelyas this point of contact is no more coincident with the top dead centerof the cam, the aforesaid three points are no more aligned and the shaft1 begins to rotate. During the first portion of this rotation the rocker16 resumes its initial position of engagement with check pin 18, thespring stacking is expanded and the thrust exerted by the actuator dropsfrom F, to F,. This rotation is continued until the roller 19 engagesthe V- shaped notch of cam 2. Then, the detent positioning action isobtained as explained hereinabove.

The chain-dotted cam contour 30 of FIG. 1 shown a modified form ofembodiment of this invention giving two predetermined angular andlocking positions for a same shaft.

This cam 30 comprises two top dead centers and two bottom dead centers.A specific and advantageous feature of this cam is that the detentposition time is reduced to one-half in comparison with the precedingform of embodiment. In fact, the maximum angle of rotation required withthis cam 30 is 90, as contrasted with the 180 necessary with cam 2.However, this modified arrangement is applicable only if a shaftposition of or 180 is contemplated in the desired mode of operation.

It is also possible to contemplate n angular positions for a shaftprovided with a cam comprising only one V shaped notch 3, by radiallydisposing n actuators about this cam.

Of course, many modifications and variations may be brought to thespecific forms of embodiment and constructional details described,illustrated and suggested hereinabove, without departing from the basicprinciple of the invention. Thus, notably, it would not constitute adeparture from this principle to use any other means for automaticallybreaking the alignment of the dead center of the cam between the axes ofrotation of the shaft and roller, when the cam is in its dead centerposition.

What is claimed as new is l. Detent positioning device for orienting andlocking a rotary member in one or a plurality of angular positions,which comprises a rotary member a cam rigid with said rotary member, aroller follower engaging the outline of said cam, an actuator urgingsaid roller follower against said cam outline, and means forautomatically displacing the point of contact between the cam and rollerso as to shift this point of contact in relation to the planecontaining-the axes of the rotary member and of the roller, when saidroller is at the top dead center of the cam.

2. Detent positioning device for orienting and locking a member rigidwith a shaft adapted to revolve freely, which comprises a cam rigid withsaid shaft and having at least one dead center whereat the distance fromthe cam outline and the axis of said shaft has its minimum value, ahydraulic actuator having its piston rod directed towards the shaftaxis, a push member slidably mounted in the piston rod of said actuator,spring means mounted in said piston rod coaxially to said push memberfor constantly urging said push member towards said cam, a strap rigidwith said piston rod and having a bottom facing said cam, a pivot pinand a check pin mounted across said strap, a rocker mounted for freepivotal motion in said strap about said pivot pin and movable angularlybetween a lower position in which it engages the bottom of said strapand an upper position in which is abutes said check pin, a rollerfollower rotatably mounted on said rocker and adapted to engage theoutline of said cam through the combined action of said actuator andsaid spring means, said rocker being adapted to remain in said upperposition in said strap as long as the actuator force is inferior to theforce of said spring means, and to assume its lower position in saidstrap while tending to release said roller from said cam outline whenthe actuator force becomes greater than the force of said spring means.

3. Device as set forth in claim 2, wherein said cam comprises a singledead center, in combination with n actuators disposed radially aboutsaid cam and adapted to lock said rotary member, for each rotationalmovement thereof in n ditferent angular positions.

1. Detent positioning device for orienting and locking a rotary memberin one or a plurality of angular positions, which comprises a rotarymember a cam rigid with said rotary member, a roller follower engagingthe outline of said cam, an actuator urging said roller follower againstsaid cam outline, and means for automatically displacing the point ofcontact between the cam and roller so as to shift this point of contactin relation to the plane containing the axes of the rotary member and ofthe roller, when said roller is at the top dead center of the cam. 2.Detent positioning device for orienting and locking a member rigid witha shaft adapted to revolve freely, which comprises a cam rigid with saidshaft and having at least one dead center whereat the distance from thecam outline and the axis of said shaft has its minimum value, ahydraulic actuator having its piston rod directed towards the shaftaxis, a push member slidably mounted in the piston rod of said actuator,spring means mounted in said piston rod coaxially to said push memberfor constantly urging said push member towards said cam, a strap rigidwith said piston rod and having a bottom facing said cam, a pivot pinand a check pin mounted across said strap, a rocker mounted for freepivotal motion in said strap about said pivot Pin and movable angularlybetween a lower position in which it engages the bottom of said strapand an upper position in which is abutes said check pin, a rollerfollower rotatably mounted on said rocker and adapted to engage theoutline of said cam through the combined action of said actuator andsaid spring means, said rocker being adapted to remain in said upperposition in said strap as long as the actuator force is inferior to theforce of said spring means, and to assume its lower position in saidstrap while tending to release said roller from said cam outline whenthe actuator force becomes greater than the force of said spring means.3. Device as set forth in claim 2, wherein said cam comprises a singledead center, in combination with n actuators disposed radially aboutsaid cam and adapted to lock said rotary member, for each rotationalmovement thereof , in n different angular positions.